I have the Lowepro Pro Trekker 300 AW bag, the same one shown in your ad, and I love it. I do a lot of hiking, snowshoeing, and canoe tripping in remote areas and this bag really keeps my equipment protected - with a few reservations. I keep bodies, lenses and other 'not waterproof' items in waterproof stuff sacks inside the camera bag. I like the rolltop stuff sacks from Sea-To-Summit which come in a variety of sizes. You don't need compression-type stuff sacks.
The ad says it is lightweight but compared to what? If you really need something lightweight, this may not be the bag for you. It is an expedition bag that will keep your equipment safe. It is heavier than most similar sized bags.
The bag comes with all sorts of bells and whistles many of which I don't really use. I've never bothered with the 'hydration pack' feature although several local outdoor stores carry packs from various suppliers like Camelback that will fit. I simply use a Nalgene water bottle. The Nalgene bottle is very 'breakproof' and I don't trust the vinyl pouches and flimsy grocery store water bottles not to puncture or break inside my camera pack.
When you get your new bag, you will need to spend some time getting it properly adjusted to fit your back. I suggest taking it to someone knowledgeable (for example at an outdoor store) to get help with that. You will also need to readjust some things for summer versus winter use.
It's a fine bag. Good luck with it.